United States: US reserves

In late 2007, the US Energy Information Administration released its estimates for US crude and gas reserves for 2006. Proved crude reserves fell over 3%, about 785 million bbl, in contrast to the 1.8% rise in 2005. For the 8th consecutive year, US natural gas proved reserves rose, reaching 3.3% in 2006, slightly lower than 2005’s 6% increase, and reserves additions replaced 136% of dry gas production.

Table 1. Crude oil proved reserves, reserves changes and production, 2006, millions bbl. Click Table to Enlarge.

Crude. The federal offshore Gulf of Mexico and Alaska accounted for the largest reserve losses, at 387 and 292 million bbl, respectively, while Oklahoma lost 61 million bbl, Texas lost 48 million bbl and California’s reserves fell 46 million bbl. Number of field extensions dropped from 805 million bbl to 504 million bbl, and new field discoveries fell also, with 30 million bbl discovered compared with 2005’s 205 million bbl, an 85% decrease.

Major gains were in Utah, with 78 million barrels added, Colorado, gaining 24 million bbl, and New Mexico, with 15 million bbl added. Minor gains were also experienced in Pennsylvania and Ohio.

Table 2. Total dry natural gas proved reserves, reserves changes and production, 2006, Bcf @ 14.73 psia and 60°F. Click Table to Enlarge.

Fewer discoveries and lower-than-average net revisions and adjustments were the principal factors in the crude reserve decline, and the low amount of new reserves only replaced 52% of crude produced in 2006.

Natural gas. Texas had the most gain in proved reserves, rising 5,329 Bcf from 2005, due primarily to field extensions. The majority of gas discoveries in 2006 came from extensions, totaling 21,778 Bcf. Extensions rose more than 3% from 2005, and were 61% higher than the previous 10-year average. Other major gains were Alaska, with 2,074 Bcf due to revisions increases, and Utah, with 851 Bcf due to new development.

Both new field discoveries and new reservoirs in old fields experienced drops in 2006, 533 and 53 Bcf, respectively, with new field discoveries 75% less than the previous 10-year average. Net negative revisions were reported for the first time since 1998, as revision decreases exceeded revision increases by 1,836 Bcf in 2006.